Wafer-level assembly method for chip-size devices having flipped chips

摘要

A method for assembling a whole semiconductor wafer ( 101 ) with a plurality of device units ( 120 ) having metal contact pads. Each contact pad has a patterned barrier metal layer and a metal stud (103, preferably copper or nickel) with an outer surface suitable to form metallurgical bonds without melting. A leadframe suitable for the whole wafer is provided, which has a plurality of segments groups ( 102 ), each group suitable for one device unit; each segment has first ( 102 a) and second ends ( 102 b) covered by solderable metal. A predetermined amount of solder paste ( 104 ) is placed on each of the first segment ends. The leadframe is then aligned with the wafer so that each of the paste-covered segment ends is aligned with the corresponding metal stud of the respective device unit. The leadframe is connected to the wafer and the whole wafer is encapsulated ( 105 ) so that the device units and the first segment ends are covered, while the second segment ends remain exposed. The encapsulated wafer is separated ( 110 ) into individual device units ( 120 ).